Fig. 6. Force–velocity relationships in frog sartorius muscle taken from (4°C) air-access control frogs, normoxic cold-submerged frogs (12–16 weeks in air equilibrated water) and hypoxic cold-submerged frogs (12–16 weeks in 60 mmHg O₂) determined using isovelocity contractions (see Appendix for experimental details). Muscle force (P) is normalised to maximal isometric force (P₀). Velocity (V) is in muscle lengths (L) s^–1. The lines are hyperbolic-linear fits for each treatment of the form V=B(1–P/P₀)/(A+P/P₀)+C(1–P/P₀) (Marsh and Bennett, 1986), calculated using the mean values for the constants A, B and C determined for each muscle for each group. Maximum shortening velocity was significantly different for the three groups (one-way ANOVA: F_1,8=4.47, P=0.05). The curvature of the force–velocity relationship (F_1,8=0.745, P=0.51) and maximum power output (F_1,8=0.832, P=0.47) were not significantly different between the three groups. (G. N. Askew and R. G. Boutilier, unpublished observations.)